Process for the preliminary treatment of raw sugar and the like



Patented Mar. 14, 1933 UNITED STATES PATENT OFFICE f JULIEN BERGE, or rliannivron'r, BELGIUM, ASSIGNOR T nnrrmnnrn rmL-EMQNTOISE,

scorers ANTONYME, or TIRDEMONT', BELGIUM, A CORPORATION PROCESS FOR "THE PRELIMINARY TREATMENT .(DF' RAW1SUGAR AND THE LIKE No Drawing. Application filed March 15, 1930, Serial No. 436,255, and in Germany August 26, 1926 This invention pertains generally to the formation of crystals from solutions. I shall describe the same in connection with the manufacture of sugar as anexample. However, it is understood that it is applicable to a large variety of other products.

The invention is applicable totheenhancing of the yield from massecuite, especially after the massecuite has been subjected to the ordinary centrifuging heretofore employed to furnish the product known in commerce as raw sugar, and to the delivery of such increased yield to the refinery in a highly pur1- fied state.

Raw sugar is generally found in commerce containing all the way from 85to 95 or 96% more or less of crystallized sugar, the rest constitutingnon-sugar elements such :as invert sugars, gums, ash, etc. and water. These non-sugar elements form a syrup which coats the individual sugar crystals and contaminates the product. This syrup, or. course, is a part of the mother syrup in Whichthe sugar crystals were formed. If the raw sugar 2 .has been manufactured in temperate climates,

or has been stored in damp. places, or subjected to moisture in transportation, or other- Wise, the watercontent of the adhering syrup is such as to hold in solution a considerable .30 amount of'sucrose or crystallizable sugar such as to raise the sugar'content of the adhering syrup above the approximate minimum towhich it is ordinarily practicable to crystallize sugar from mother syrup. In

-3 ordinary practice when this syrup is removed from the crystals it is necessary to reprocess the. same inorder to extract therefromthis excess sugar. This, of course, consumesconsiderable time, is laborious and expensive,.and

' results in sugar losses.

On the other hand if the raw sugar has been produced in hot, dry climates, .or is otherwise rapidly dried, .thesyrup adhering to the crystals has given up more water than isrequired to hold the same in solution, and thus forms a sort of lacquer aroundthe'sugar crystals. This so-called lacquer contains considerable sugar which would otherwise be crystallizable except for the rapid drying. The

sugar content of this dried syrup or so-called lacquer, is, theref0re,-also higher than the approximate minimum to which it is ordinarily practicable to impoverish mother syrup. I y

The removal of either this so-called lacquer, or the first mentioned crystal coating syrup, from the sugar crystals has required operations such as washing with water or steam or with syrups, such as highly purified syrups or syrups of various stages of purity, etc. All washing mediums carry awayfin solution a portion of the crystallized sugar, thus further reducing the yield, and making necessary further processing directed to- Ward the recovery of suchsugar losses.

The removal of substantially all of the adhering syrup is highly desirable before be ginning refining operations, among other things, not only' because the syrup discolors the sugar crystals, but because the removal of as much of the as'hias possible provides a high saline co-eflicient; that is a high ratio of sugar to the salts contained in the mass to be refined. In beetsugar manufacture, for instance, when the mother liquor of the re-' finery has been impoverished to the extent 5 that its sugar divided by'its ash is approximately equalto 5, more or-less, it has generally been considered impracticable to attempt to further reduce the sugar content of the mother liqor by the ordinary sugar boiling, methods.

The presence of invert sugars also presents crystallization difiiculties. This offers an additional reason for desiring to remove-as much as possible of the adhering syrup from y the raw sugar before beginning refiningiop- "erations.

, The centrifugals used heretofore operate at aspeed such that the centri-fugalfforce generated is sufficient to remove syrup from syrup, but leave a film of syrup adhering to the sugar crystals even though centrifuging-takes place when the mass is relatively warm. The mass is ordinarily held at temperatures between 50 to 60 C. during centrifuging. These centrifugals exert a centrifugal force in the neighborhood of 500 to 6.00 times the weight of the mass. .As above pointed out, washing operations are necessarily resorted to in order .to remove the remaining film of syrup from the crystals. This washingyof course, redissolves 7 Well as to deliver such crystallized sugar to the, refinery in a highly purified state, I sub j ect the raw sugar to certain processes wherec by the water content of the adhering syrup app'roache'sa value at which such water content is substantiallyjust suificient to hold in solutiomat'a desired temperature, the nonsugar constituents of the syrupand the percentage of sugar that is to be left in the syrup.- In other words, the water content of the syrup approaches the value at which Y itis substantially just "suflicient to hold in solution, at a desired temperature, the nonsugar constituents ofthe final molasses, and the'percentage ofsugar that is to be left injthe molasses. :It follows that the rest of thesugar in the syrup is available for crystallization, and such crystallization is materially aided by the presence of. the very large. number ofsugar crystals onto which such sugar readily deposits.

.1 The amount of sugar which is to be left in the molasses is; determined by experience in the;.art, is more or less a function of the impurities present and'is generally ,a PIiLClZl.

crystallization. a The amount of water to be added or sub cably irreducible minimum beyond which the labor, tim'eand expense in trying to eflect furthercrystallization by the ordinary sugar p boiling methods isnot warranted by the small further yield thus obtained. i

If the adhering syrup contains more than the desired amountof water, it is desiccated,

Whereas if the adhering syrup contains less than the desired amount of water it is moistened' suificiently to bring itto the desired state. The moistening of the: syrup frees the sugar formerly held fast in the lacquer-like coating, and makes such sugar available'for tracted from a particular batchof raw sugar may be ascertained. upon an analysis of a sample, or empirical means maybe devised for this purpose. For instance let us assume for the purpose of illustration that a sample of a batch of raw sugar is ofthe following composition: 1

Polarization; Q 95. Water s; i; 2.26 Non sugar 2.74

Let it be assumed that it is desirable to p obtain a molasses having a purity equal to 62 and that centrifugal separation is to take place at a temperature of 20 centigrade. It

is generally understood that at a tel nperature of approximately 20 C. and a purity ores,

one kilogram of water will dissolve 2.62 kilograms of sugar in addition to the nonsugar constituents. Tables for other temperatures and purities can be obtained or readily prepared. From this the following is derived: j

The purity of a syrup or molasses is equal Substituting the'data of th'eJexample under consideration We obtain 100 X 2.62 non-sugar By transposingwe obtain I rag a-222.25% no ing 2.62kilograms of sugar, is-as follows:

100x262 Non-sugar tof'water, hereafter referred to as the con centration of non-sugargis therefore equal to Non-sugar; 1.61 kilograms 61 Water 1 kilogram To obtain molasses having a purityof 62 when the centrifuging is to take place at ap-- proximately 20 C. the concentration of the non-sugar should be 1.61" according to this calculation. if

of molasses canbe readily prepared.

The concentration of non-sugar in the sample of raw sugar above mentioned is as follows:

Concentration of 'non-sugar= 1 Non-sugar 2.74 21 Water 2.26

' tis readily seen that thewater content of the batch of raw sugar under consideration must be. reduced so that the concentration of non-sugar may approach 1.61.

If one kilogram is the quantity of water required in a quantityof syrup containing 1.61 kilograms of non-sugar in order that the syrup may retain in solution suflicient sugar to have a purity of 62, the quantity of water required in a quantityof syrup containing 2.74 kilograms of non-sugar is b ='1.70 kilograms of water.

' It is, therefore, seenthat from each 100 Tables for other temperatures andpurities H -2. 2=4.232.e2 =1.e1 kg. 7 The concentration of non-sugar with respect 7 p ioo kilograms of raw suga'r corresponding to the above sample, it is necessary to extract 2.26-1.70=0.56 kilograms of water. Upon the reduction of the water content by 0.56 kilograms the centesimal composition of the raw sugar is approximately as follows Polarization; 95. 535 Water 1.710 Non-Sugar 2.755

In checking the latter formula we find that the concentration of non-sugar is as follows:

from any particular batch of raw sugar whether beet, cane, or otherwise, inorder to obtain molasses of any desired purity, can be either calculated,v or empirically determined by persons skilled in'the art and familiar with this invention.

It is to be understood, however, that all calculations and empirical determinations are merely estimates and aresubject to actual operating conditions. The characteristics of different, batches of raw sugar vary, and, therefore, the exact amount of water to be added or to be removed from the adhering syrup of a particular batch, to obtain molassesof the exact purity desired, may require actual trial accompanied by an analysis of the final molasses. The water content of the adhering syrup is then raised or lowered in accordance with the invention herein disclosed.

Furthermore this invention is not limited to optimum conditions, that is to the presence of the exact amount of water desired, but includes all desiccating and/or moistening of raw sugar to obtain an increased yield. Manyforms of apparatus may be usedin carrying out this process. For instance, the raw sugar may be placed in an ordinary storeroom in sacks, These sacks may be arrangedin such a way as to permit more or less free circulation of air of the desired moisture content between and around the sacks. Relatively dry or relatively moist air may then be circulated through the storeroom according to whether the Water content of the adhering syrup is to be lowered or raised.

The-temperature of the storeroom may be regulated by regulating the temperature of the circulating air, or by entirely independent devices such as radiators, steam coils, etc. For instance, it might be desirable to hold the raw sugar at one temperature and circulate the air at another temperature, especially to bring about, or regulate the rate of, a change in the degree of saturation of the air coming in contact with the sugar. The storeroom may be at the temperature at which centrifuging is to take place, or may be at any other temperature, or series of temperatures, at the time of moistening or of desiccating of the syrup, and then may be brought to the desired centrifuging temperature at some time before the centrifuging takes place. The regulation of moisture and temperature is somewhat a matter of'choice to obtain conditions con-v ducive-to maximum crystallization. For instance, slow' cooling with slow evaporatlon of water is considered conducive to this end. Y

In the case of moistening dry syrup the temterature and moisture content may if desired, be raised above that at which the sugar is to be centrifuged, and then loweredfi'Howeverthis is not necessary, and may not even be desirable in many instances.

.Any means may be employed to determine when the moistening or desiccating should be stopped, such as taking samples foranalysis at desired intervals, etc. or automatic means may bedevised for this purpose. Automatic means may also be devised for regulating the temperature of the storeroom. Any form of chamber or storeroom may be employed, which is preferably, though not necessarily,

closed. The sugar need not be in sacks, but

may be in piles, spread out in layers, or may be in any other form or condition suitable for the results desired.

After the syrup has reached the desired state the raw sugar is centrifugedin centrifugals in which it is subjected to centrifugal forces much higher than heretofore employed.

The centrifugals generally operate with forces substantially between 1200 to 7000 (or more) times the weight of the mass centrifuged but may operate with a force as low as 800 as disclosed in my co-pending applicationSerial No. 167,598, which has resulted in Patent No. 1,775,385, and are capable of sep arating substantially all of the syrupfrom the sugar crystals, apparently without regard to ordinary temperatures and viscosities of the syrup. The forces generated in these centrifugals overcomethe, adherence of the syrup for the sugar crystals, thus effecting a substantially complete separation'of the former from the latter. Owing to the high centrifugal forces employed the sugar may be centrifuged at relatively low'temperatures, that is, at temperatures much lower than heretofore employed, thus permitting an unusually high degree of crystallization. Centrifuging may take placeat 20 C. or in many cases at temperatures even lower. l-lowevencentrifuging may take place at other temperatures if desired.

Even though centrifuging in my process may takeplace at sub-normal temperatures,

masses containing crystal flour of foam orboth are satisfactorily handled, and the syrup thrown off contains very little crystal flour. This is a distinct improvement over the centrifuging heretofore practised in which crystal flour heretofore the crystal flour and syrup formed into ball-like 'masses from which the crystal .fiour could not be discharged. In my process such ball-like masses, if formed, are broken up by the extremely high centrifugal forces used, and the syrup is driven from the crystal flour.

7. 7 ,Owing to thesubstantially complete crystallization of sugar from the syrup and the substantially complete separation of the molasses (exhausted syrup) from the crystal lized sugar, an unusually high yield of raw sugar is deliyered to the refinery. This sugar "is in a high state of purification thus permit- E ting an unusually high degree of crystallisation in the refining processes. In many 1nstances thesugar is in such a highly purified state that for many purposes further refining is unnecessary.

It is, of course, understood that although the use of water, steam, syrup of high purity r or syrup at various states of purity, etc. in the centrifugals to assist in the separation of the syrup is in most instances unnecessary, the

same may beemployed if desired. Ordinary-v runaoff liquor from the centrifugals, in the event that washing is not resorted to, is molasses of substantially the desiredsugar content.

In the use of high centrifugal force I have accomplished what has been considered throughout the sugar industry as impossible, to wit, actual separation of adhering syrup from sugar crystals without washing.

have accomplished thiseven though centrifuging takes place at relatively low temperatures, that is,nb-elow temperatures of to 0., at which centrifuging has taken place heretofore, particularly when syrups of low purity were discharged.

I have found that the degree to which syrup is discharged from the crystals is not directly proportional .to the centrifugal force employed, but that at certain centrifugal forcesin excess of those used prior to'my invention there are large increases in the degree to which the syrup is discharged. Furthermore I have found that the syrup discharged does not act asa homogeneous whole as has been heretofore supposed, but that its composition differs at various centrifugal forces-up to the maximum necessary to effect complete separation. f Analyses of the discharged syrup at various centrifugal forces show thatvarious constituents of the syrup centrifugal force the same is true of'the ash as well as other constituents. By this means, therefore, it is possible to reduce the proportion of a particular constituent in the discharged syrup by collecting in a separate container the syrup thrown off at the critical let-go point for that constituent. On the other hand the proportion of the particular constituent in the syrup collected in the separate container is relatively high. It is, of V course, understood that a separate container may be used at any number or all critical points if desired. By this means agradu-' atedseparation of the constituents of the adhering syrup is made possible.

A graduated separation of the syrup into portions having a relatively high proportion of a particular constituent is of value for instance in the processes for the extraction of further sugar from the molasses. The proportions of organic, saline, or other impurities which prevent crystallization of the sugar in themolasses' may be reduced in this manner, or the proportion of the particular impurity having the greatest effect upon crystallization may be reduced. 1

The phenomena of surface adherence between syrup and crystal are not a mere matter of surface tension or of capillary attraction in the interstices formed by the crystals,

but involve adsorption and possibly other phenomena.

The crystals are not crushed ordeformed by the centrifugal forces employed and, although the total space between the crystals decreases somewhat, a point is finally reachedbeyond which no further decrease takes place and at which the syrup can still be effectively removed from the crystals.

It is understood that theterm raw sugar as used herein includes not only first, second and third sugars but any type of sugar hav-,

ing adhering particles,'and whet-her raw, refined, or otherwise.

Having descrlbed my invention, it is obvious that many modifications may be made in the same such as the adding, eliminating or changing the order of or varying the degree of certain steps in the process; using any other gas in place of air; moistening with any other solvent for thesugar; applying the invention to the crystallization of other products in which case the air or other gas may be saturated or partially saturated with water,

or any other solvent desired, etc. using other devices in place of centrifugals employing for instance linear, transverse, circuitous or reciprocatory motion; moistening or desiccating beyond the desired point and then returning to such point; using temperatures above or below those for which calculations have been made; moistening or desiccating at certain rates, or variety of rates, and at certain, or a variety of, temperatures, above or below the final temperature; etc. etc. Without departing from the spirit of the invention. Reference is made to my copending generic application, Serial Number 167,597, filed February 11, 1927 which has resulted in Patent No. 1,809,807.

I claim:

1. The process of reducing the sugar content of dried syrup adhering to sugar crystals in raw sugar comprising placing said sugar in an enclosure, moistening said syrup to bring it to a fluid-like state and regulating the temperature and moisture content of said syrup to reduce the sugarcontent thereof by crystallization, and then removing the syrup from the sugar crystals.

2. The process of reducing the sugar content of dried syrup adhering to sugar crystals in raW sugar comprising placing said sugar in an enclosure, moistening said syrup to bring it to a fluid-like state and regulating the temperature and moisture content thereof by regulating the temperature and moisture content of the air in said enclosure to reduce the sugar content of the syrup by crystallization, and then removing the syrup from the sugar crystals.

3. The process of reducing the sugar content of dried syrup adhering to sugar crystals in raw sugar comprising placing said sugar in an enclosure, moistening said syrup to bring it to a fluid-like state, and regulating the moisture content thereof to reduce the sugar content of the syrup by crystallization, and then removing the syrup from the sugar crystals.

4. The process of reducing the sugar content of dried syrup adhering to sugar crystals in raw sugar comprising placing said sugar in an enclosure, moistening said syrup to bring it to a fluid-like state and regulating the moisture content thereof by regulating the moisture content of the air in said enclosure to reduce the sugar content of the syrup by crystallization, and then removing the syrup from the sugar crystals.

5. The process of reducing the sugar content of dried syrup adhering to sugar crystals in raw sugar comprising placing said sugar in an enclosure, moistening said syrup. to bring it to a fluid-like state and regulating the temperature and moisturecontent of said syrup to reduce the sugar content thereof by crystallization, and then removing the syrup from the sugar crystals by the use of a centrifugal force sufliciently high to overcome the adherence of substantially all of the syrup to the sugar crystals.

6. The process of reducing the sugar content of dried syrup adhering to sugar crystals in raw sugar comprising placing said sugar in an enclosure, moistening said syrup to bring it to a fluid-like state and regulating the temperature and moisture content thereof by regulating the temperature and moisture content of the air in said enclosure to reduce the sugar content of the syrup by crystallization, and then removing the syrup from the sugar crystals bythe use of a centrifugal force sufficiently high to overcome.

the adherence of substantially all of the syrup to the sugar crystals.

7. The process of reducing the sugar c011- tent ofdried syrup adhering to sugar crystals in raw sugar comprising placing said sugar in an enclosure, moistening said syrup to bring it to a fluid-like state, and regulatmg the moisture content thereof to reduce the sugar content of the syrup by crystallization,

and then removing the syrup from the sugar crystals by the use of a centrifugal force sufficientlyhigh to overcome the adherence of substantially all of the syrup to the sugar crystals.

S. The processof reducingthe sugar content of dried syrup adhering to sugar crystals in raw sugar comprising placing said sugar in an enclosure, moistening said syrup to bring it to a fluid-like state and regulating the moisture content thereof'by regulating the moisture content of the air in said en JULIEN BERGE. 

